Laminated ceramic substrate and manufacturing method therefor

ABSTRACT

A laminated ceramic substrate includes a side electrode in which a side edge electrode layer formed on a side edge portion of a ceramic layer overlaps with and connects to a side edge electrode layer formed on a side edge portion of another ceramic layer directly above and/or directly below the former ceramic layer. The side edge electrode layer includes a parallel wall unexposed and approximately parallel to a side surface of the laminated ceramic substrate and a perpendicular wall approximately perpendicular to the side surface of the laminated ceramic substrate. A length La of the parallel wall and a depth Lb of the parallel wall from the side surface of the laminated ceramic substrate have a relationship of La&gt;Lb.

TECHNICAL FIELD

The present invention relates to a laminated ceramic substrate forconstituting various electronic circuits provided in electronic devicessuch as portable telephones, and to a manufacturing method therefor.

BACKGROUND ART

Conventionally, in a small electronic device such as a portabletelephone, it has been carried into practice that a plurality of circuitelements constituting, the device are integrated in one-chip laminatedceramic component and the laminated ceramic component is mounted on amain substrate (Patent Document 1, for example).

FIG. 11 illustrates a laminate structure of a laminated ceramiccomponent 1, in which a plurality of ceramic layers 2 are laminated toconstitute a laminated ceramic substrate 20. Formed on each surface ofthe ceramic layers 2 are a plurality of circuit element patterns 3constituting an inductor or a capacitor. These circuit element patterns3 are connected to each other by a vertical conduction path (hereinafterreferred to as a via hole) 31 formed by penetrating the ceramic layers2. A side electrode 47 is provided on a side surface of the laminatedceramic substrate 20 and connected to the circuit element patterns 3.

A cavity 21 is provided on a surface of the laminated ceramic substrate20. An electronic component 4 such as a surface acoustic wave filter ismounted on a bottom surface of the cavity 21. The electronic component 4is connected to the circuit element patterns 3 through a bonding wire32.

A lid 5 covering the cavity 21 is placed on the surface of the laminatedceramic substrate 20 to constitute the laminated ceramic component 1packaged.

The above-described laminated ceramic substrate 20 is manufactured bythe steps shown in FIG. 10.

First, as shown in FIG. 10( a), a green sheet 25 including a ceramicmixed material is prepared. Next, as shown in FIG. 10( b), a throughhole 22 for a cavity, a through hole for a via hole (not shown), and acircular-shaped through hole 23 for a side electrode are provided atdesired locations of the green sheet 25. Thereafter, as shown in FIG.10( c), the through hole for a via hole and the through hole 23 for aside electrode are filled with a conductive material 24. Subsequently,as shown in FIG. 10( d), the conductive material 24 is printed on asurface of the green sheet 25 to form a circuit element pattern 30.

Green sheets 25 thus obtained are laminated and thereafter integrated byheat press or other methods to prepare a green-sheet laminated body 26shown in FIG. 10( e).

Thereafter, as shown in FIG. 10( f), the green-sheet laminated body 26is divided for each cavity 21 to obtain a plurality of green-sheetlaminated body chips 27. Then, as shown in FIG. 10( g), each of thegreen-sheet laminated body chips 27 is fired to obtain the laminatedceramic substrate 20.

As shown in FIG. 11, the electronic component 4 is mounted on the bottomsurface of the cavity 21 of the laminated ceramic substrate 20 thusobtained. Then wire bonding is applied thereto and the lid 5 is placedto thereby complete the laminated ceramic component 1.

[Patent Document 1] U.S. Pat. No. 3,336,913, FIG. 6(b)

A conventional laminated ceramic substrate includes a semicircular sideelectrode in which a side edge electrode layer formed on a side edgeportion of a ceramic layer overlaps with and connects to a side edgeelectrode layer formed on a side edge portion of another ceramic layerdirectly above and/or directly below the former ceramic layer. This canbe obtained because a circular-shaped through hole for a side electrodeis filled with a conductive material and thereafter divided. FIG. 4( a)is a partial top view in the vicinity of a circular-shaped through hole23 for a side electrode of a conventional green-sheet laminated body 26.Through holes 23 a, 23 b, and 23 c for a side electrode each have thesame shape. For example, a green sheet 25 a is disposed on a designedcenter in a side-electrode width direction and on a designed center in aside-electrode depth direction with a green sheet 25 b laminated thereonshifted from the designed center in the side-electrode width directionto the left in the drawing by X1 greater than the radius of the throughhole for a side electrode and a green sheet 25 c further laminatedthereon shifted from the designed center in the side-electrode widthdirection to the right in the drawing by X2 greater than the radius ofthe through hole for a side electrode. The green sheets 25 b and 25 care both disposed on the designed center in the side-electrode depthdirection. A width direction center of the through hole 23 a for a sideelectrode of the green sheet 25 a is the same as the designed center 43in the side-electrode width direction. In contrast, a width directioncenter 42 b of the through hole 23 b for a side electrode of the greensheet 25 b is shifted from the designed center 43 in the side-electrodewidth direction to the left in the drawing by the shift amount X1. Awidth direction center 42 c of the through hole 23 c for a sideelectrode of the green sheet 25 c is also shifted from the designedcenter 43 in the side-electrode width direction to the right in thedrawing by the shift amount X2.

FIG. 4( b) is a partial side view in the vicinity of a side electrode ofa green-sheet laminated body chip 27 obtained by dividing thegreen-sheet laminated body 26 along a line 45 a-45 a (same as thedesigned center 45 in the side-electrode depth direction). As seen inthe drawing, side edge electrode layers 41 a, 41 b, and 41 c that mustessentially be electrically connected are disconnected at a borderbetween the neighboring side edge electrode layers 41 b and 41 c of thegreen sheets 25 b and 25 c, respectively, resulting in a laminatedceramic substrate with a disconnection defect.

FIG. 6( a) is a partial top view in the vicinity of a circular-shapedthrough hole 23 for a side electrode of a conventional green-sheetlaminated body 26. Through holes 23 d, 23 e, and 23 f for a sideelectrode each have the same shape. For example, a green sheet 25 d isdisposed on a designed center in a side-electrode width direction and ona designed center in a side-electrode depth direction with a green sheet25 e laminated thereon shifted from the designed center in theside-electrode depth direction to the bottom in the drawing by Y3smaller than the radius of the through hole for a side electrode andshifted from the designed center in the side-electrode width directionto the left in the drawing by X3 smaller than the radius of the throughhole for a side electrode, and with a green sheet 25 f further laminatedthereon shifted from the designed center in the side-electrode depthdirection to the top in the drawing by Y4 smaller than the radius of thethrough hole for a side electrode and shifted from the designed centerin the side-electrode width direction to the right in the drawing by X4smaller than the radius of the through hole for a side electrode. Adepth direction center and a width direction center of the through hole23 d for a side electrode of the green sheet 25 d are the same as thedesigned center 45 in the side-electrode depth direction and thedesigned center 43 in the side-electrode width direction, respectively.In contrast, a depth direction center 44 e of the through hole 23 e fora side electrode of the green sheet 25 e is shifted from the designedcenter 45 in the side-electrode depth direction to the bottom in thedrawing by the shift amount Y3 and a width direction center 42 e of thethrough hole 23 e for a side electrode of the green sheet 25 e isshifted from the designed center 43 in the side-electrode widthdirection to the left in the drawing by the shift amount X3. A depthdirection center 44 f of the through hole 23 f for a side electrode ofthe green sheet 25 f is also shifted from the designed center 45 in theside-electrode depth direction to the top in the drawing by the shiftamount Y4 and a width direction center 42 f of the through hole 23 f fora side electrode of the green sheet 25 f is also shifted from thedesigned center 43 in the side-electrode width direction to the right inthe drawing by the shift amount X4.

FIG. 6( b) is a partial side view in the vicinity of a side electrode ofa green-sheet laminated body chip 27 obtained by dividing thegreen-sheet laminated body 26 along a line 45 b-45 b (same as thedesigned center 45 in the side-electrode depth direction). As seen inthe drawing, even if each of the shift amounts Y3 and Y4 in the depthdirection and each of the shift amounts X3 and X4 in the width directionof the green sheets 25 e and 25 f are both smaller than the radius ofthe side electrode, side edge electrode layers 41 d, 41 e, and 41 f thatmust essentially be electrically connected are disconnected at a borderbetween the neighboring side edge electrode layers 41 e and 41 f of thegreen sheets 25 e and 25 f, respectively, resulting in a laminatedceramic substrate with a disconnection defect.

FIG. 8( a) is a partial top view in the vicinity of a circular-shapedthrough hole 23 for a side electrode of a conventional green-sheetlaminated body 26. Through holes 23 m, 23 n, and 23 o for a sideelectrode each have the same shape. For example, green sheets 25 m and25 o are shifted from a designed center in a side-electrode depthdirection to the top in the drawing by Y5 smaller than the radius of thethrough hole for a side electrode with a green sheet 25 n laminatedthereon shifted from the designed center in the side-electrode depthdirection to the bottom in the drawing by Y6 greater than the radius ofthe through hole for a side electrode. The green sheets 25 m, 25 n, and25 o are all disposed on the designed center in the side-electrode widthdirection. Depth direction centers 44 m and 44 o of the through holes 23m and 23 o for a side electrode of the green sheets 25 m and 25 o areshifted from the designed center 45 in the side electrode-depthdirection to the top in the drawing by the shift amount Y5. A depthdirection center 44 n of the through hole 23 n for a side electrode ofthe green sheet 25 n is also shifted from the designed center 45 in theside-electrode depth direction to the bottom in the drawing by the shiftamount Y6.

FIG. 8( b) is a partial sectional view in the vicinity of a sideelectrode in which the green-sheet laminated body 26 is divided along aline 43 c-43 c (same as the designed center 43 in the side-electrodewidth direction). As seen in the drawing, the through holes 23 m, 23 n,and 23 o for a side electrode that must essentially be electricallyconnected are disconnected at a border between the neighboring throughholes 23 m and 23 n for a side electrode of the green sheets 25 m and 25n, respectively, and at a border between the neighboring through holes23 n and 23 o for a side electrode of the green sheets 25 n and 25 o,respectively. A side electrode of a green-sheet laminated body chip 27obtained by dividing the green-sheet laminated body 26 along a line 45c-45 c (same as the designed center 45 in the side-electrode depthdirection) is to be disconnected, resulting in a laminated ceramicsubstrate with a disconnection defect.

As described above, there has been a problem that a disconnection defectcaused by lamination shift may reduce production yield of a laminatedceramic substrate 20.

Accordingly, an object of the present invention is to provide alaminated ceramic substrate and a manufacturing method therefor in whichoccurrences of a disconnection defect of a laminated ceramic substrate20 caused by green sheet lamination shift are reduced.

DISCLOSURE OF THE INVENTION

The side edge electrode layer includes a parallel wall unexposed andapproximately parallel to a side surface of the laminated ceramicsubstrate and a perpendicular wall approximately perpendicular to theside surface of the laminated ceramic substrate. A length La of theparallel wall and a depth Lb of the parallel wall from the side surfaceof the laminated ceramic substrate have a relationship of La>Lb. Amanufacturing method includes a step shown in FIG. 10( b) of providing athrough hole for a via hole and a through hole 23 for a side electrodeat desired locations of a green sheet 25, in which the through hole 23for a side electrode has at least four straight-line portions as shownin FIG. 3( a).

FIG. 3( a) is a partial top view in the vicinity of a through hole 23for a side electrode of a green-sheet laminated body 26 of the presentinvention. Through holes 23 g, 23 h, and 23 i for a side electrode eachhave the same shape, and a depth direction dimension thereof (dimensionbetween 46 a-46 a) is equal to the diameter of the circular-shapedthrough hole for a side electrode in FIG. 4. A length of two oppositeflat walls 46 a of the through hole for a side electrode is greater than½ of the dimension between the flat walls 46 a-46 a. Each of shiftamounts of three green sheets from a designed center in a side-electrodewidth direction and from a designed center in a side-electrode depthdirection is also exactly the same as that in FIG. 4. That is, a greensheet 25 g is disposed on the designed center in the side-electrodewidth direction and on the designed center in the side-electrode depthdirection with a green sheet 25 h laminated thereon shifted from thedesigned center in the side-electrode width direction to the left in thedrawing by X1 greater than ½ of the depth of the through hole for a sideelectrode and a green sheet 25 i further laminated thereon shifted fromthe designed center in the side-electrode width direction to the rightin the drawing by X2 greater than ½ of the depth of the through hole fora side electrode. The green sheets 25 h and 25 i are both disposed onthe designed center in the side-electrode depth direction. A widthdirection center of the through hole 23 g for a side electrode of thegreen sheet 25 g is the same as the designed center 43 in theside-electrode width direction. In contrast, a width direction center 42h of the through hole 23 h for a side electrode of the green sheet 25 his shifted from the designed center 43 in the side-electrode widthdirection to the left in the drawing by the shift amount X1. A widthdirection center 42 i of the through hole 23 i for a side electrode ofthe green sheet 25 i is also shifted from the designed center 43 in theside-electrode width direction to the right in the drawing by the shiftamount X2.

FIG. 3( b) is a partial side view in the vicinity of a side electrode ofa green-sheet laminated body chip 27 obtained by dividing thegreen-sheet laminated body 26 along a line 45 a-45 a (same as thedesigned center 45 in the side-electrode depth direction). As seen inthe drawing, neighboring side edge electrode layers 41 h and 41 i of thegreen sheets 25 h and 25 i, respectively, partially overlap to preventthe disconnection at the border found conventionally, free from adisconnection defect.

FIG. 5( a) is a partial top view in the vicinity of a through hole 23for a side electrode of a green-sheet laminated body 26 of the presentinvention. Through holes 23 j, 23 k, and 23 l for a side electrode eachhave the same shape, and a depth direction dimension thereof (dimensionbetween 46 b-46 b) is equal to the diameter of the circular-shapedthrough hole for a side electrode in FIG. 6. A length of two oppositeflat walls 46 b of the through hole for a side electrode is greater than½ of the dimension between the flat walls 46 b-46 b. Each of shiftamounts of three green sheets from a designed center in a side-electrodewidth direction and from a designed center in a side-electrode depthdirection is also exactly the same as that in FIG. 6. That is, a greensheet 25 j is disposed on the designed center in the side-electrodewidth direction and on the designed center in the side-electrode depthdirection with a green sheet 25 k laminated thereon shifted from thedesigned center in the side-electrode depth direction to the bottom inthe drawing by Y3 smaller than ½ of the depth of the through hole for aside electrode and shifted from the designed center in theside-electrode width direction to the left in the drawing by X3 smallerthan ½ of the depth of the through hole for a side electrode, and with agreen sheet 25 l further laminated thereon shifted from the designedcenter in the side-electrode depth direction to the top in the drawingby Y4 smaller than ½ of the depth of the through hole for a sideelectrode and shifted from the designed center in the side-electrodewidth direction to the right in the drawing by X4 smaller than ½ of thedepth of the through hole for a side electrode. A depth direction centerand a width direction center of the through hole 23 j for a sideelectrode of the green sheet 25 j are the same as the designed center 45in the side-electrode depth direction and the designed center 43 in theside-electrode width direction, respectively. In contrast, a depthdirection center 44 k of the through hole 23 k for a side electrode ofthe green sheet 25 k is shifted from the designed center 45 in theside-electrode depth direction to the bottom in the drawing by the shiftamount Y3 and a width direction center 42 k of the through hole 23 k fora side electrode of the green sheet 25 k is shifted from the designedcenter 43 in the side-electrode width direction to the left in thedrawing by the shift amount X3. A depth direction center 44 l of thethrough hole 23 l for a side electrode of the green sheet 25 l is alsoshifted from the designed center 45 in the side-electrode depthdirection to the top in the drawing by the shift amount Y4 and a widthdirection center 42 l of the through hole 23 l for a side electrode ofthe green sheet 25 l is also shifted from the designed center 43 in theside-electrode width direction to the right in the drawing by the shiftamount X4.

FIG. 5( b) is a partial side view in the vicinity of a side electrode ofa green-sheet laminated body chip 27 obtained by dividing thegreen-sheet laminated body 26 along a line 45 b-45 b (same as thedesigned center 45 in the side-electrode depth direction). As seen inthe drawing, neighboring side edge electrode layers 41 k and 41 l of thegreen sheets 25 k and 25 l, respectively, partially overlap to preventthe disconnection at the border found conventionally, free from adisconnection defect.

FIG. 7( a) is a partial top view in the vicinity of a through hole 23for a side electrode of a green-sheet laminated body 26 of the presentinvention. Through holes 23 p and 23 r for a side electrode each havethe same shape, and a depth direction dimension thereof (dimensionbetween 46 c-46 c) is equal to the diameter of the circular-shapedthrough hole for a side electrode in FIG. 8. A depth direction dimensionof a through hole 23 q for a side electrode (dimension between 46 d-46d) is greater than the diameter of the circular-shaped through hole fora side electrode in FIG. 8. A length of two opposite flat walls 46 c ofeach of the through holes 23 p and 23 r for a side electrode is greaterthan ½ of the dimension between the flat walls 46 c-46 c. A length oftwo opposite flat walls 46 d of the through hole 23 q for a sideelectrode is greater than ½ of the dimension between the flat walls 46d-46 d. Each of shift amounts of three green sheets from a designedcenter in a side-electrode width direction and from a designed center ina side-electrode depth direction is also exactly the same as that inFIG. 8. That is, green sheets 25 p and 25 r are shifted from thedesigned center in the side-electrode depth direction to the top in thedrawing by Y5 smaller than ½ of the depth of the through hole 23 p for aside electrode with a green sheet 25 q laminated thereon shifted fromthe designed center in the side-electrode depth direction to the bottomin the drawing by Y6 greater than ½ of the depth of the through hole 23p for a side electrode. The green sheets 25 p, 25 q, and 25 r are alldisposed on the designed center in the side-electrode width direction.Depth direction centers 44 p and 44 r of the through holes 23 p and 23 rfor a side electrode of the green sheets 25 p and 25 r are shifted fromthe designed center 45 in the side-electrode depth direction to the topin the drawing by the shift amount Y5. A depth direction center 44 q ofthe through hole 23 q for a side electrode of the green sheet 25 q isalso shifted from the designed center 45 in the side-electrode depthdirection to the bottom in the drawing by the shift amount Y6.

FIG. 7( b) is a partial sectional view in the vicinity of a sideelectrode in which the green-sheet laminated body 26 is divided along aline 43 c-43 c (same as the designed center 43 in the side-electrodewidth direction). As seen in the drawing, the neighboring through holes23 p and 23 q for a side electrode of the green sheets 25 p and 25 q,respectively, and the neighboring through holes 23 q and 23 r for a sideelectrode of the green sheets 25 q and 25 r, respectively, eachpartially overlap. Thus, a side electrode of a green-sheet laminatedbody chip 27 obtained by dividing the green-sheet laminated body 26along a line 45 c-45 c (same as the designed center 45 in theside-electrode depth direction) is prevented from disconnections at theborders, resulting in a laminated ceramic substrate free from adisconnection defect.

As described above, a side edge electrode layer including a parallelwall unexposed and approximately parallel to a side surface of alaminated ceramic substrate and a perpendicular wall approximatelyperpendicular to the side surface of the laminated ceramic substrate, inwhich a length La of the parallel wall and a depth Lb of the parallelwall from the side surface of the laminated ceramic substrate have arelationship of La>Lb, can decrease an occurrence rate of disconnectionsof a side electrode caused by lamination shift, and therefore candecrease disconnection defects of the laminated ceramic substrate toimprove production yield of the laminated ceramic substrate.

FIG. 9( a) is a front view of a laminated ceramic substrate 20. FIGS. 9(b) to (d) are schematic sectional views in which the laminated ceramicsubstrate 20 is divided along a line 60-60. A side edge electrode layer47 is only shown for simplification of the drawings.

Odd number green sheets from the top layer provided with a through holefor a side electrode having a double depth of a depth Lb of the sideedge electrode layer and even number green sheets from the top layerprovided with a through hole for a side electrode having a greater depththan that of the through hole for a side electrode of the odd numbergreen sheets are laminated alternately to complete the laminated ceramicsubstrate. FIG. 9( b) shows a cross section of the laminated ceramicsubstrate, in which ceramic layers 2 a with a side edge electrode layer41 having a smaller depth and ceramic layers 2 b with a side edgeelectrode layer 41 having a greater depth are alternated from the toplayer to the bottom layer, that is, a sum of depths of opposite sideedge electrode layers 41 LbL+LbR partially differs with respect to alaminated direction. This can further decrease an occurrence rate ofdisconnections of a side electrode caused by lamination shift.

As shown in FIG. 9( c), a side edge electrode layer 41 having a greaterdepth may be provided only on a ceramic layer 2 c formed with a greensheet that may easily cause lamination shift such as a thin green sheetor a green sheet having a large area GND pattern printed thereon. A sideedge electrode layer 41 having a greater depth may also be provided onlyon a layer directly above and/or directly below the ceramic layer 2 c asshown in FIG. 9( d).

The number and position of ceramic layers provided with a side edgeelectrode layer 41 having a greater depth are not limited, butpreferably, the number of ceramic layers provided with a side edgeelectrode layer 41 having a greater depth is limited to a minimumnecessary because a side edge electrode layer 41 with a greater depthmakes narrower an area in which a circuit element pattern 3 is disposedon the ceramic layers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 includes a partial top view and a partial perspective viewaccording to Example 1 of the present invention;

FIG. 2 includes a partial top view and a partial perspective viewaccording to Example 2 of the present invention;

FIG. 3 illustrates one step of a laminated ceramic substrate of thepresent invention;

FIG. 4 illustrates one step of a laminated ceramic substrate of aconventional example;

FIG. 5 illustrates one step of a laminated ceramic substrate of thepresent invention;

FIG. 6 illustrates one step of a laminated ceramic substrate of aconventional example;

FIG. 7 illustrates one step of a laminated ceramic substrate of thepresent invention;

FIG. 8 illustrates one step of a laminated ceramic substrate of aconventional example;

FIG. 9 includes a front view and schematic sectional views of alaminated ceramic substrate of the present invention;

FIG. 10 illustrates a series of the steps of a laminated ceramicsubstrate of the present invention and a conventional example; and

FIG. 11 is a sectional view of a laminated ceramic component using alaminated ceramic substrate of the present invention and a conventionalexample.

BEST MODE FOR CARRYING OUT THE INVENTION

A description of embodiments of the present invention will be givenbelow with reference to the drawings.

A laminated ceramic substrate 20 of the present invention is constitutedby laminating a plurality of ceramic layers 2 as shown in FIG. 11.Formed on each surface of the ceramic layers 2 are a plurality ofcircuit element patterns 3 constituting an inductor or a capacitor. Thecircuit element patterns 3 are connected to each other by a via hole 31formed by penetrating the ceramic layers 2. A side electrode 47 isprovided on a side surface of the laminated ceramic substrate 20 andconnected to the circuit element patterns 3. A cavity 21 is provided ona surface of the laminated ceramic substrate 20.

A laminated ceramic component 1 using the laminated ceramic substrate 20has an electronic component 4 such as a surface acoustic wave filtermounted on a bottom surface of the cavity 21. The electronic component 4is connected to the circuit element patterns 3 through a bonding wire32. A lid 5 covering the cavity 21 is placed on the surface of thelaminated ceramic substrate 20 to constitute the laminated ceramiccomponent 1 packaged.

The above-described laminated ceramic substrate 20 is manufactured bythe steps shown in FIG. 10.

First, as shown in FIG. 10( a), a green sheet 25 including a ceramicmixed material is prepared. Next, as shown in FIG. 10( b), a throughhole 2 for a cavity, a through hole for a via hole, and a through hole23 for a side electrode are provided at desired locations of the greensheet 25.

The through hole for a via hole and the through hole 23 for a sideelectrode of a plurality of green sheets 25 thus obtained are filledwith a conductive material 24.

Thereafter, a circuit element pattern 30 is printed on a surface of theplurality of green sheets 25 with the conductive material 24. The greensheets 25 thus obtained are laminated and integrated by heat press orother methods to prepare a green-sheet laminated body 26.

Next, as shown in FIG. 10( f), the green-sheet laminated body 26 isdivided for each cavity 21 to obtain a plurality of green-sheetlaminated body chips 27. Then, as shown in FIG. 10( g), each of thegreen-sheet laminated body chips 27 is fired to obtain the laminatedceramic substrate 20.

EXAMPLE 1

FIG. 1( a) is a partial top view in the vicinity of a side electrode ofa laminated ceramic substrate according to the present invention. FIG.1( b) is a partial perspective view in the vicinity of the sideelectrode of the ceramic substrate. Provided on a side surface of thelaminated ceramic substrate 20 is a side electrode 47 in which side edgeelectrode layers 41 overlap and connect from the top layer to the bottomlayer. The side edge electrode layer includes a parallel wall unexposedand approximately parallel to the side surface of the laminated ceramicsubstrate and a perpendicular wall approximately perpendicular to theside surface of the laminated ceramic substrate. A length La of theparallel wall and a depth Lb of the parallel wall from the side surfaceof the laminated ceramic substrate have a relationship of La>Lb.

Furthermore, the parallel wall and perpendicular wall are connected by acorner portion 46 with an R-shape. Failure to provide the R-shape mayeasily cause a shortage of a conductive material 24 because the cornerportion 46 without the R-shape is difficult to fill with the conductivematerial 24. This may decrease a contact area after firing between aconductive material side wall and ceramic side wall of the sideelectrode 47 of the laminated ceramic substrate 20, resulting in lowpeel strength of the side electrode 47 against the ceramic part.Moreover, an attempt to completely fill the corner portion 46 with theconductive material 24 may complicate the management of the filling stepto lower the productivity. Therefore, preferably, the corner portion 46has an R-shape like the present example. The range of R is sufficient ifgreater than 0.02 mm.

EXAMPLE 2

FIG. 2( a) is a partial top view in the vicinity of a side electrode ofa laminated ceramic substrate according to a second example of thepresent invention. FIG. 2( b) is a partial perspective view in thevicinity of the side electrode of the ceramic substrate. In the sideelectrode on a side surface of the laminated ceramic substrate 20, thetop layer fails to have a side edge electrode layer, but each layer fromthe second top layer to the bottom layer has a side edge electrodelayer. The present example shows the top layer without a side edgeelectrode layer, but a layer without a side edge electrode layer is notlimited to the top layer and may be another layer or a plurality oflayers.

In the present examples, the green-sheet laminated body 26 is dividedand thereafter fired, but the same effect can of course be obtained evenif the green-sheet laminated body 26 is fired and thereafter divided.Furthermore, the filling of the through hole for a via hole and thethrough hole 23 for a side electrode with the conductive material 24 maybe performed simultaneously with the printing of the circuit elementpattern 30 on the surface of the green sheet 25 with the conductivematerial 24.

Embodiments of the present invention are described above specificallywith examples, but the present invention is not limited to theseexamples.

INDUSTRIAL APPLICABILITY

The present invention can decrease an occurrence rate of disconnectionsof a side electrode caused by lamination shift, and therefore candecrease disconnection defects of a laminated ceramic substrate toimprove production yield of the laminated ceramic substrate.

1. A laminated ceramic substrate formed by laminating a plurality ofceramic layers, the laminated ceramic substrate including a sideelectrode comprising a side edge electrode layer formed on a side edgeportion of at least one of the ceramic layers which overlaps with andconnects to a side edge electrode layer formed on a side edge portion ofan adjacent ceramic layer directly above and/or directly below the atleast one ceramic layer, each side edge electrode layer being within athrough hole in the ceramic substrate, the through hole defined by aside surface of the laminated ceramic substrate, a wall approximatelyparallel to the side surface of the laminated ceramic substrate and twoperpendicular walls approximately perpendicular to the side surface ofthe laminated ceramic substrate, a length La of the parallel wall and adepth Lb of the parallel wall from the side surface of the laminatedceramic substrate having a relationship of La>Lb.
 2. A laminated ceramicsubstrate according to claim 1, wherein each perpendicular wall isconnected to the parallel wall by a corner portion with a circular-arcshape of a radius R in which R is greater than 0.02 mm.
 3. A laminatedceramic substrate formed by laminating a plurality of ceramic layers,the laminated ceramic substrate including opposite side electrodes eachcomprising a side edge electrode layer formed on a side edge portion ofat least one of ceramic layers which overlaps with and connects to aside edge electrode layer formed on a side edge portion of an adjacentceramic layer directly above and/or directly below the at least oneceramic layer, each side edge electrode layer being within a throughhole in the ceramic substrate, the through hole defined by a sidesurface of the laminated ceramic substrate, a wall approximatelyparallel to the side surface of the laminated ceramic substrate and twoperpendicular walls approximately perpendicular to the side surface ofthe laminated ceramic substrate, a length La of the parallel wall and adepth Lb of the parallel wall from the side surface of the laminatedceramic substrate having a relationship of La>Lb.
 4. A laminated ceramicsubstrate according to claim 3, wherein each perpendicular wall isconnected to the parallel wall by a corner portion with a circular-arcshape of a radius R in which R is greater than 0.02 mm.
 5. A laminatedceramic substrate according to claim 3, wherein the amount of the depths(LbL+LbR) of opposite side edge electrode layers on at least one ceramiclayer differs from the amount of the depths (LbL+LbR) of opposite sideedge electrode layers on the other ceramic layers.
 6. A laminatedceramic substrate according to claim 4, wherein the amount of the depths(LbL+LbR) of opposite side edge electrode layers on at least one ceramiclayer differs from the amount of the depths (LbL+LbR) of opposite sideedge electrode layers on the other ceramic layers.